Paper tape, a relatively strong length of paper commonly used for bailing pulp, severing paper webs, and for other uses in the paper industry or other industries, may be formed by bonding a number of paper yarns together along their lengths with an adhesive. Various methods and devices have been used in the past to create the paper yarns used to form the paper tape. Many of these methods and devices involved twisting a thin paper strip about its longitudinal axis to form the yarn as the strip is pulled from a roll of paper (also referred to as a paper “pad”). The pad is formed by wrapping the strip around a tubular core.
Two types of previous yarn twisting devices are “tree twisters” and “ring twisters.” The tree and ring twisters both position the pad vertically and pull the strip from the pad's outer circumference. As the device pulls the strip downward from the pad (rotating the pad about a horizontal axis), it twists the strip to form the yarn.
Tree and ring twisters may be undesirable. Ring twisters require that the pad be extensively moistened before beginning the twisting process, which adds an extra step prior to the twisting process and also may require that the yarn be dried after the twisting, before gluing it up into paper tape. Tree twisters are relatively slow—they cannot be stably run at high speeds and also have a tendency to break the paper strip at high speeds. Ring twisters can be run at higher speeds than tree twisters (but not necessarily as fast as twisters in accordance with some of the embodiments of the present invention described below), but they have other undesirable aspects. For instance, ring twisters produce a relatively unsmooth yarn and require that the yarn be collected on a vertical cylinder referred to as a “bobbin.” Yarn collected on a bobbin may need to be unrolled to dry thoroughly to be used effectively in subsequent processes for forming the paper tape.
Another previous yarn twisting device is a “bowl twister.” Unlike tree and ring twisters, the bowl twister positions the pad horizontally, inside a large bowl. Also unlike the tree and ring twisters, the bowl twister does not pull the strip from the outer circumference of the pad, but pulls the strip from the inner circumference of the pad. The bowl rotates as the strip is pulled down through a hole in the bottom of the bowl, facilitating twisting the strip into yarn. Bowl twisters secure the pad by snugly mounting the pad into a bore in the bowl.
Bowl twisters may also be undesirable. Fitting the pad snugly into the bore of the bowl requires that the pad be manufactured with a precise outside diameter. It is difficult, however, to manufacture a pad with a precise outer diameter, requiring that outer layers of the pad be removed (creating excessive waste) or that the pad be shimmed (a difficult and time consuming process) to make the pad fit snugly. Also undesirably—pads that are shimmed may not be able to be run stably at high speeds in a bowl twister.